FIG. 1 schematically shows a typical power converter arrangement for a high-power application. The power converter arrangement has a frame 2 that houses two identical power converter devices 3 (for redundancy reasons).
Each power converter device 3 has a housing 4 that houses a static switching element bridge 5 each having a multi-phase ac input 6 (such as a three phase input) connected to a multi-phase ac voltage supply 7, and a dc output connected via dc connections 8 to a load, e.g. the field windings of the synchronous generator.
Each housing 4 is provided with a cooling system 9 that typically includes one or more fans that urge cooling air through the housing 4 for it to cool the static switching element bridge 5 contained therein.
Each static switching element bridge 5 is composed of 2×n switching elements 10, exemplarily represented by thyristor symbols, where n denotes the number of phases of the multi-phase ac input 6. The switching elements 10 may be power semiconductor switches such as diodes, thyristors, gate-turn-off thyristors (GTOs), bipolar junction transistors, or insulated gate bipolar transistors (IGTBs).
The redundancy of the power converter bridges 5 is such, that each static switching element bridge 5 alone is able to carry the rated current of the system.
In normal operation, one of the two static switching element bridges 5 is active and carries 100% of the system current and the other is in standby (i.e. it does not operate).
In case a fault is detected in the active static switching element bridge 5, it is blocked and the standby static switching element bridge is activated.
Even if the traditional arrangements proved to be quite effective in operation, nevertheless they require a large space for their installation, in particular because (for redundancy reasons) they include two power converter devices 3. In a power plant space is typically limited and costly, in particular in zones close to the synchronous generator; thus positioning of a bulky component could be troubling and expensive.
In addition, the costs of the arrangements are quite high, in particular because the power converter devices 3 are expensive and the arrangements include two of them.